4.1 D

- UNIT

RATES

LESS

ON 4-1

D

MRS. W

ILSON

WHAT DOES RATE MEAN?

The unit rate is the rate for one unit of a given quantity. Unit rates have a denominator of 1.

The word PER means 1 !!!!

A rate is a RATIO that compares two things that have DIFFERENT units!

Ex: Students per Bus OR Miles per Hour

GOING FROM RATE TO UNIT RATE

Rate: 150 heartbeats2 minutes

just DIVIDE to get the Unit Rate!!!

150 ÷ 2 = 75 heartbeats per minute.

See how there are 2 different units of measure?

150 heartbeats in 2 minutes

You can also write it as…

75 heartbeats / minute

FIND THE UNIT RATEAmy can read 88 pages in 4 hours. What is the unit rate?

(How many pages can she read per hour?)

88 pages4 hours

88 ÷ 4 = 22

So…

22 pages per hour

or 22 pgs / hr

1 hr

Notice that hours turns to 1…that is the number you divide by!

NOT ALL RATES WILL BE EVEN NUMBERS!

It is $30 for 4 t-shirts. What is the unit rate?

$30 4 shirts

30 ÷ 4 = 7.5

You have to add a decimal and a zero!!

How much $ is this?

1 shirt

$7.50 for each shirt!

SOMETIMES YOU KNOW THE UNIT RATE ALREADY…

Joe’s car goes 20 miles per gallon of gasoline. How far can it go on

8 gallons of gasoline?

20 miles1 gallon

*Per Means 1.

Here’s what it looks like!

=8 gallons

x 8x 8

x 8x 8

20 x 8 = 160. Joe’s car can go 160 miles on 8 gallons of gas.

SOMETIMES YOU KNOW THE UNIT RATE ALREADY…

It costs $15.50 per student for the trip. If there are 20 students going, how

much will the total be?

$15.50 1 student

*Per Means 1.

Here’s what it looks like!

=20 students

x 20x 20

x 20x 20

15.50 x 20 = 310. So it will cost $310 for 20 students to go.

It’s easy to remember:

If you need to FIND a UNIT rate, you DIVIDE

If you already KNOW the Unit Rate, you MULTIPLYIf you are ever unsure WHICH number to divide by, find the measure that will become a 1. This measure is what you divide by!!!